Safety alarm



y 4, 1955 A. M. NEWHALL, JR 2,709,210

SAFETY ALARM Filed April 10, 1955 IN VEN TOR.

EC/(HOFF 5' SLICK A MEMBER OF THE FIRM SAFETY ALARM Almer M. Newhall, Jr., Sonoma, Calif.

Application April 10, 1953, Serial No. 347,924

2 Claims. (Cl. 200-142) This invention relates to a device for protecting a machine or other device from an excessively high temperature. The device has its primary application to internal combustion engines, but, as will be later apparent, it can be applied to a variety of devices wherein one wishes to either shut off the device or to provide an alarm for excessively high temperatures, such as in a hot air furnace.

Various devices have been proposed in the past for the protection of engines and the like from excessive emperatures. Such devices heretofore proposed have ordinarily employed bimetallic elements or other forms of expansion elements, such as a liquid column. Such devices are not positive in operation in that the vibration or" the machine being protected quite often interferes with the proper function, or causes a premature function of the safety device. Further, such devices are ordinarily fairr expensive to manufacture and are not entirely trustworthy in operation due to corrosion.

it is an object of the present invention to provide a safety device which employs no moving parts, which is inexpensive to manufacture and which is absolutely foolproof in its operation.

Another object of this invention is to provide an engine shut-off which is positive in operation, which operates through the electrical ignition system of the engine, and which will cause no damage to the ignition system.

Referring to the drawings forming a part of this application,

Figure 1 shows the device of the present invention attached to the head of an internal combustion engine and the method of wiring the device, in schematic form.

Figure 2 is a cross-section in elevation of the device of the present invention.

Figure 3 is a plan view in cross-section of the device of the present invention on the lines 3--3 of Figure 2.

Figure 4 is a View of the device of the present invention showin, in schematic form, the method by which the device can be used as a warning indicator and the like.

Referring now to the drawings by reference characters, the device of the present invention has been generally indicated 5 and consists of a bracket 5, which is attached to the head 7 of an internal combustion engine by means of one of the head bolts 9. It is obvious that the bracket 5 could be an integral part of the head 7, or of the block of the engine, but it has been illustrated as being a detachable part since the device in this form lends itself to being added to existing engines. Further, the bracket 5 may be of any suitable shape for attachment to various engines. The bracket member 5 is of any suitable heat conducting metal such as steel, copper, aluminum, or the like. The bracket 5 is provided with a hole iii, in which is inserted a snug fitting washer-like annular member 13, which is made of a fusible alloy, as hereinafter defined. The central aperture of the member 13 is of such size that a bolt or rivet 17 may be inserted therethrough without contacting the member 13. Two insulators 19 are provided which form a tight fit hired States Patent 0 2,709,210 Patented May 24-, 1955 with the bolt or rivet 17. It will be noted that the insulators 19 have an annular recess 21, which fits the member 13 snugly and that the member 13 is slightly thicker than the bracket 5. In this way, the parts are held rigidly in place and there is no possibility of the bolt or rivet 17 contacting the metal insert 13. However, if the bracket 5 is heated to the fusing point of the alloy 13, the alloy 13 will melt, completing the circuit between the bolt 17 and the bracket 5.

in Figure 1, there is shown, in schematic manner, the method of connecting the device to an ordinary spark-ignited internal combustion engine employing a coil and a battery. In this application, one of the terminals 23 of the battery 25 is grounded, while the opposite terminal is connected to ignition switch 27. The switch 27 leads to the primary winding 29 of a spark coil and the other terminal of the primary 29 is connected to the breaker switch 31 of the distributor, which is actuated by cam 33. The breaker switch 31 is bypassed by a condenser 35'. The coil has a secondary 37, which is connected to the distributor or spark plug through line 39 in the conventional manner.

According to this embodiment of the invention, a wire 41 is brought from the bolt or rivet 17 through a soldering lug 43, to the breaker switch 31, as illustrated. It is obvious that in this embodiment, the device of the present invention has no effect on the normal starting and running of the engine, but if the engine over-heats so that the alloy ring 13 melts, the coil 29 will be grounded, stopping the action of the engine. It is also obvious in this embodiment there is no injury to the ignition system since coil 29 can stand the primary current flowing without injury. If a magneto is used instead of a battery, the connection to the primary system is the same as is shown in Figure 1.

In engines employing dual ignition, the fusible alloy ring 13 may have two holes therethrough, as would the insulators 19, so that two bolts or rivets 17 could be used. In this manner, both sides of the ignition system would be cut off when the member 13 fused, yet there would be no connection between the two ignition systems when the device was in the normal condition.

In the drawing it will be noted that in each instance the actual fusible element is spaced some distance from the point of attachment to the engine block. Since the bracket is of relatively thin construction and is exposed to circulation of air, it serves as a time delay element so that even if the engine should overheat momentarily, fusion will not immediately be produced, but there will be a slight time delay. Thus, the engine will not be needlessly shut off when a harmless momentary overload occurs.

The composition of the alloy ring 13 can be selected depending upon the particular application of the device. in other words, alloys of different temperature characteristics can be seiected, depending upon the temperature at which one wishes the device to become operative. In an ordinary liquid cooled internal combustion engine a temperature of slightly above the boiling point of water is entirely suitable for the cut-oif actuation and an alloy fusing at, say, 216 F. can be used. Such an alloy can be made by compounding 53.9% bismuth, 25.9% tin, and 20.2% cadmium. In engines operating at slightly higher temperatures, such as those employing pressure radiators, an alloy composed of 44.5% lead and 55.5% bismuth, which fuses at 250 1 has been found suitable. It is obvious to those skilled in the art that any number of alloys can be used, depending upon the exact temperature desired for actuation.

Although this invention has been described primarily in connection with a conventional liquid-cooled sparkignited internal combustion engine, it is obvious that ice other engines such as diesel engines, air-cooled engines, aircraft engines, and the like may be similarly protected. Further, the device may be used with gas turbine engines, hot air furnaces, steam boilers and the like for either effecting a shut-ofif, or the actuation of an alarm.

In Figure 4, there is shown the general circuit which may be employed for many purposes. In this circuit, a device to be protected such as a furnace or engine, is provided with the safety device 6, which is wired to an alarm or indicating device 49, to a battery 55, one side of which is grounded at 47 The box indicated at 49 may be a visible we rig 2 ch as a light or a flasher, a horn for sounding an audible warning, or may be a shut-off device to the systems fuel supply, r the like.

In some instances, it is advantageous to provide two of the devices 6, one of which fuses at a lower temperature than the other. Thus, one of the devices might sound a warning to indicate a slight overload, while the second device would be set to fuse at a slightly higher temperature and to possibly stop operation of an engine in the event the first warning signal was ignored.

I claim:

1. A device of the character described, comprising a fiat metal bracket having a circular aperture therein, a mounting hole spaced therefrom, said bracket serving as a time delay element, a fiat, washer-like member of a fusible alloy fitting snugly in said aperture, said memher being thicker than said bracket, a contact member passing through the center of the washer-like member and spaced therefrom, two substantially identical insulators held by said central contact member, each insulator having an annular recess which fits snugly on the periphery of the washer-like member, one of said insulators being located on each side of said bracket and said washer-like member whereby the insulators serve to hold the washer-like member and the central contact member in fixed relationship to the bracket.

2. A device of the character described, comprising a fiat metal bracket having a circular aperture therein, a mounting hole spaced therefrom, said bracket serving as a time delay element, a fiat, washer-like member of a fusible alloy fitting snugly in said aperture, a contact member passing through the center of the washer-like member and spaced therefrom, two substantially identical insulators held by said central contact member, one of said insulators being located on each side of said bracket and said washer-like member whereby the insulators serve to hold the washer-like member and the central contact member in fixed relationship to the bracket.

References Cited in the file of this patent UNITED STATES PATENTS 995,221 Britain et al. June 13, 1911 1,239,830 Sheldon Sept. 11, 1917 1,348,338 Vandergrift Aug. 3, 1920 1,825,052 Cleveland Sept. 29, 1931 1,856,715 Lyndon May 3, 1932 2,516,964 Derby et al. Aug, 1, 1950 

